The exhaustion of the address space of the internet protocol version 4 (IPv4) has been a concern for decades. Early predictions warned that IPv4 would have been depleted years ago. In 2011, by some measures, some parts of the world have depleted their IPv4 supply. However, the transition to Internet Protocol Version 6 (IPv6) is just beginning to gain momentum. Until IPv6 becomes pervasive, the use of IPv4 addresses for service delivery will continue to dominate.
The address space of IPv6 has about 3.4×1038 addresses, which provides flexibility in address allocation and theoretically sufficient for every person on earth to be allocated millions of unique addresses. A large number of people may access the Internet using several devices, each of which may have a unique address under IPv6 rather than relying on network address translation, in which all of the devices in a local network appear to have the same address to the rest of the Internet. However, until the infrastructure of the Internet has transitioned to IPv6, services relying on IPv4 will remain ubiquitous. Thus, mobile devices may include dual IPv4 and IPv6 functionality. IPv4 addresses cannot be permanently assigned to every device, however, the IPv6 functionality, may be leveraged to expand the reach of IPv4 services.